package 代码随想2._5双指针法;

/**
 * @author XXX
 * @date 2024-01-17 15:48
 */

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * https://leetcode.cn/problems/3sum/description/
 */
public class _9三数之和 {
    public List<List<Integer>> threeSum(int[] nums) {
        List<List<Integer>> res = new ArrayList<>();
        Arrays.sort(nums);

        for (int i = 0; i < nums.length; i++){
            if (nums[i] > 0)
                return res;
            if (i>0 && nums[i]==nums[i-1])
                continue;

            int left = i+1;
            int right = nums.length - 1;
            while (right > left){
                int sum = nums[i] + nums[left] + nums[right];
                if(sum > 0)
                    right--;
                else if(sum<0)
                    left++;
                else{
                    res.add(Arrays.asList(nums[i],nums[left],nums[right]));
                    // 去重逻辑应该放在找到一个三元组之后，对b 和 c去重
                    while (right > left && nums[right] == nums[right - 1]) right--;
                    while (right > left && nums[left] == nums[left + 1]) left++;

                    right--;
                    left++;
                }
            }
        }
        return res;
    }
}
